A major problem of the 21st century will be sufficient food and feed for a growing global population. At the current world population growth rate of about 80 million people per year, food production must increase 20% in developed countries and 60% in developing countries to just keep pace with current food consumption. The rapidly increasing GDPs of China and India are raising the standard of living such that current food consumption levels will become unacceptable to more people and food production will have to be further increased.
Some estimate that 90% of the world's arable land is already cultivated (not counting forests and unsuitable areas), although food yields from agriculture in Africa are far below European, U.S. and even Chinese yields and some arable African land is under exploited. However, about 24 million acres of arable land are abandoned each year due to salinization and other physical/chemical degradations. Food production could be increased if crop productivities can be maintained in spite of land salinization and aridity.
The identification and use of salt/drought tolerance and fruit sweetness are important to plant husbandry and crop production, particularly for commercial crop production in agronomy and horticulture.
Past researchers have used salt-tolerant and salt-sensitive plant models in attempts to find salt and drought tolerance genes. For example, expression profiling studies have identified hundreds of genes that are regulated differently in salt-tolerant vs. salt-sensitive plant species and almost 100 of these genes have been cloned into salt-sensitive model plants and shown to increase salt tolerance. However, to date, none of these efforts have led to the ability to develop salt-tolerant cultivated plant species.
Fruit sugar content is a trait of interest to tomato breeders. Fruit sugar contributes to flavor, so is commercially valuable. Fruit sugar content is three times higher in the Galapagos tomato than the cultivated tomato (Balibrea et al., 2006). This trait has been shown to vary in other wild tomato species as well (Fridman el al., 2000). A single QTL accounts for most of the variation in this trait between cultivated tomato and S. pennellii (Fridman et al., 2000), suggesting that a single gene may explain a substantial part of differences in fruit sugar content.
The present invention provides for the identification, characterization and use of tomato genes that control salinity tolerance, drought tolerance and fruit sugar content (i.e., fruit sweetness).